Telegraphy.



No. 778,177. PATENTED DEC. 20', 1904.

T. B. DIXON.

TELEGRAPHY.

APPLICATION FILED APR. 22, 1902.

2 SHEETS-SHEET 1.

N0 MODEL.

E E W/TNESSES: A & INVENTOI? I v 1 V ATTORNEYS I PATENTEDYDEG. 20, 1904.'T. B. DIXON.

TELEGRAPHY.

APPLICATION FILED APR. 22, 1902.

2 SHEETS-SHEET 2.

N0 MODEL.

'- W/TNESSES;

, INVENTOH 7 a TTORNEYS Patented December 20, 1904.

PATENT OFFICE.

THOMAS B. DIXON, on NEW YORK, iv. Y.

TELEGRAPHY.

SPECIFICATION forming part of Letters Patent No. 778,177, dated December20, 1904. I Original application filed October 11, 1898, Serial No.693,205. Divided and this application filed April 22, 1902. Seriallie-104,154.

.To a whom it may concern:

va citizen of the United States, residing at New York, in the county ofNew York and State of New York, have invented certain new and usefulImprovements in Telegraphy; and I do hereby declare the followingto'be afull, clear, and exact description of the invention, such as will enableothers skilled in the art to which it appertains to' make and use thesame.

My invention relates generally to signaling systems, and particularly toimprovements in systems of multiplex telegraphy whereby a plurality ofdistinct and separate messages may be transmitted simultaneously over asingle wire or conductor or over a submarine cable.

My invention, resides in a novel system of transmitting two telegraphicmessages simultaneously in the same direction over a single line wireor, conductor, which may be combined with other well-known systems ofduplex telegraphy, so as to permit the simultaneous transmission of anequal number of messages in the opposite direction.

The objects of my invention are, first, to improve multiplex signalingsystems, and particularly multiplex systems of telegraphy, and render itpossible to operate such multiplex systems over longer lines and withgreater rapidity than has been practicable with former systems, to avoidall interference between the messages transmitted, and to avoidinterference with the transmission due to leakage, mutilation ofsignals, induction, and similar disturbing causes; second, to render itpracticable to transmit two messages simultaneously in the samedirection and an equal number of messages in the opposite direction overlong submarine-cable lines, which cannot be done with the systems ofmultiplex telegraphy now in use on such lines, and, third, to make thesystem assimple as possible.

These objects are attained in the systems of signaling, particularlyadapted for telegraphic signaling, herein described, apparatus andcircuits for which are illustrated in the drawings which accompany andform a part of this specificatlon. v

In the drawings, Figure 1 is a diagram 1llustrating an arrangement ofcircuits and instruments for transmitting two simultaneous messages overa single line conductor in one direction. Fig. 2 is a diagramillustrating the arrangement of circuits and transmitting and receivinginstruments at one end of a quadruplex line, the arrangement of circuitsand transmitting and receiving instruments being similar to those shownin Fig. 1.

In the duplex and quadruplex telegraph systems herein described all ofthe signals are transmitted by pulsatory currents, each signal beingtransmitted by two pulses, one at the beginning and the other at the endof the signal. One transmitter atthe end of the line produces positivepulses only in the line, the other transmitter producing only negativepulses. spond to the said transmitters are operated one by positivepulses only and the other by, negative pulses only, each relay beingchanged from and restored to normal condition by alternate pulses ofthat polarity by which said relay may be operated.- Interference withthe operation of the receiving instruments at one end of the line by thecurrents produced by the operation of the transmitting instruments atthe same end of the line is prevented by any of the ordinary methods ofduplex telegraphy.

Referring now to the drawings, and first of The two receiving-relayswhich re-' all to Fig. 1, which illustrates the, arrange- I ment ofcircuits and instruments for diplex telegraphy over land lines and shortsubmarine-cable lines, A is a transmitting-station, and B areceiving-station, at opposite ends of a line-wire L. O and D aretransmitting instruments, andE a selecting instrument, at thetransmitting end of the line,'and F and Gare receiving-relays at thereceiving end of the line. H and I are line batteries or generatorsoppositely connected to the line, so as to furnish thereto currents ofopposite direction, andK a localbattery or generator of thetransmitting-station which supplies current for circuits connecting theselectorE and the transmitting instruments O and D. Other batteries atthe transmitting-station are local to the instruments to which they'areconnected and will be mentioned hereinafter.

The function of transmitter C is to place battery H to the line for aninstant at the beginning and again at the end of each signal sentthrough that transmitter, and similarly the function of transmitter D isto place battery I to the line momentarily at the beginning and again atthe end of each signal sent through that transmitter. Since bothbatteries may not be connected with the line simultaneously without eachneutralizing the effect produced by the other, the selector E isemployed to give precedence automatically to one battery, placing theother battery to the line as soon as the pulse from the battery havingpreced enee is completed. The selector consists of a main or selectingrelay. M and a vibrator N, itself composed of two polar relays 1 and 2,which alternately reverse each other, thus producing exceedingly rapidvibration of their armatures. The circuits of or controlled by selectorE are as follows: The positive pole of battery K is connected to thearmature 3 of the relay 1. To the two contact-stops of this armature areconnected the local-circuit conductors 4E and 5, leading to opposingmagnet-coils of relay 2 and thence to a returnconductor 6, leading tothe negative pole of battery K. The one circuit or the other is completeaccording to with which contaet-stop the armature 3 makes contact at anyinstant.

To the armature 7 of relay 2 is connected the local-circuit conductor 8,connected to one set of coils of relay 1 and thence to batteries 9 and10, oppositely placed, which are connected each to one of thecontact-stops of armature 7. Circuit4 when complete tends to movearmature 7 to the left, so as to complete circuit 8 through battery 9,and circuit 8 when completed through battery 9 tends to move thearmature 3 of relay 1 to the right, so completing circuit 5. tends tomove armature 7 to the right, so completing circuit 8 through battery10, and since battery 10 is placed oppositely to battery 9 thecompletion of circuit 8 through battery 10 tends to deflect the armature3 to the left again. hen two polar relays are connected together in thisWay, each reversing the other, their armatures vibrate with greatrapidity, particularly if the armatures be light and their stopsadjusted so as to permit only a small amplitude of movement. Such avibrator is preferable for use in my system to vibrators consisting ofspring-reeds electrically driven, because when either armature is ineither of its extreme positions no tendency exists for it to move to theopposite position until the polarity of its magnets has been reversed,and if such reversal of the magnets of one of the relays be prevented atany instant as, for instance, by energizing other coils of the relay,which exert a preponderating influence on the armature-the vibration ofthe armatures ceases instantly, to be resumed instantly when the circuitexerting such preponderating in- Circuit 5 when complete.

fluence is broken; but I do not limit myself to the use of this type ofvibrator.

Transmitters G and D are exactly similar in construction, and thecircuits by which they are connected to selector E are similar. Onlytransmitter U need be described. It consists of polar relays 11 and 12,a handkey 13, and suitable circuits now to be described.

From conductor 4 a branch conductor 14; leads through coils of relays1and M to a contact-tongue of hand-key 13, forming a part of transmitterC. The coils of relays 1 and M, through which this circuit 14- passes,are so wound that when energized the armature i) of relay 1 is held tothe left and the armature 15 of relay M is moved to the left. The coilsof relay 1, through which circuit 11 passes, exert a stronger influenceupon the armature 2% when energized than do the coils through whichcircuit 8 passes. This is indicated in the drawings by showing thebattery Ii as made up of a greater number of cells than batteries 9 and10. Key 13 has contact-points similar to the contact-points of anordinary continuity preserving transmitting relay that is to say, it hasa spring contact-tongue 16, mounted upon a movable lever 17, having acontact point or hook adapted to make contact with the tongue, and astationary con tact-point 18, adapted to make contact with thecontact-tongue when the key is depressed and to move the tongue awayfrom the contact-hook. To the lever 17 of key 13 is connected aconductor 19, leading through coils of relay 11 to the left-handcontact-stop of relay 12. Normally conductors 14; and 19 are incommunication, their circuit being broken at relay 12, the armature 20of said relay being in contact with its right-hand contact-point. To thecontact-point 18 of key 13 is connected a conductor 21, leading throughcoils of relay 11, which oppose those coils to which conductor 19 isconnected to the right hand contact-point of relay 12. To thecontact-stops of the armature 22 of relay 11 are connected batteries orgenerators 2 and 24;, the poles of which are oppositely placed. both ofthese batteries being connected to a conductor 25, leading through coilsof relay 12 to the armature 22. \Vhen the circuit 25 is complete throughbattery 24-, it tends to move the armature 20 to the right and hold itin that position, and when complete through battery 23 said circuittends to move the armature 20 to the left and to hold it in thatposition. Relay 12 is very quick-acting, having a very light armature,while relay 11 is slower acting, its armature having upon it a weight26, by moving which along the armature the speed of the relay may beadjusted.

\Vhen key 13 is depressed, its contacts 16 and 18 make contact, and ifthe armature i be then in contact with its left-hand contact-stopcircuit 14. is completed through conduct-or 21,

thereafter, since it is in rapid vibration.

armature 20, and a return-conductor 27, connected to thereturn-conductor 6,- which leads 'to the negative pole of battery K. Ifarmature 3 be not in contact with its left-hand contact-stop at the veryinstant when contact is made between contacts 16 and 18 of key 13, itwill be in contact therewith an instaAnt s soon as the circuit 14 iscomplete armatures 3 and 7 stop vibrating and the armature-15 of relay Mmoves to' the left, as does the armature 22 of relay 11. As soon asarmature 22 reaches its lefthand contact-stop it completes circuit'25through battery 23, thus reversing relay 12 and breaking circuit 14.Armatures 3 and 7 of relays 1 and 2 then commence vibrating again. Whenthe key 13 is released, contact-tongue 16 and contact-hook 17 makecontact, completing circuit 14- through c'onductor 19, armature 20, andreturn-conductors 27 and 6, if as soon as armature 3 is in contact withits left-hand contact-stop and the armature 22 of relay 11 is deflectedto the right, circuit 14 remaining complete, however, until armature 22has reached its right- 7 hand contact-stop and by completing circuit .25through battery 24 has reversed relay 12.

depressed and again when key 13 is released,

as shown above,) armature 15 is moved to the left until it makes contactwith its left-hand contact-point, to be returned to central position assoon as circuit 14 is broken. To the left-hand contact-stop of armature15 is connected the positive pole ofline-battery H, and to the armatureitself is connected the line conductor L. When key 13 is depressed andagain when key 13 is released, therefore, battery H is placed to theline momentarily, so

producing in the line a momentary current pulsation'of positivepolarity.

A conductor 29, branching from conductor 5, passes-through magnet-coilsof relays. 1 and M, these coils being wound, however,-so as to holdarmature 3 and deflect armature 15 to the right when energized, and saidconductor isconnected to the contact-tongue of the key 13 of transmitterD. When said key is de pressed and again when itis released, thearmature of relay M is moved to the right, and since the right-handcontact-stop of said relay is connected to. the negative pole oflinebattery I said battery is placed to, the line momentarily when thekey is depressed and again when it IS released, so produclng 1n the l1nea momentary current pulsation of negative polarity. Both batteries H andI may v ing it to be placed to the line before the other battery issoplaced and holding. back the pulse from the second battery until thepulse from the first battery is completed. Which of the two batteries isthus given precedence depends upon whether the armature ,3 of relay 1 ofthe selector makes contact with its righthand stop or with its left-handstop the instant after the'keys are depressed. With whichever stop itfirst makes contact it is held in contact therewith until the pulse fromthe corresponding battery-Flor I is completed that is to say, until thearmature 22 of the relay 11 of the corresponding transmitter hasreversed the relay 12 of the transmitter. As soon as one pulse has beencompleted, so that the armature 3 is released, it moves to the oppositecontact-stop, and so permits the pulsations of current from the otherbattery to pass through the line. I

If one transmitting-keyis depressed after the other transmitting-key hasbeen depressed and after the line-battery controlled thereby has beenplaced to the line, the placing to the line of that line-battery whichcorresponds to the transmitting-key last depressed willbe delayed untilthe battery corresponding to the transmitting-key first depressed hasbeen cut out of the line by the operation of its transmitter. The lengthof the current pulsations produced by the operation of the transmittersis so brief as compared with the length of a dot of the telegraphic codethatthe slight delay in'the production of a pulsation from one of thebatteries due to the selecting action of the selector E, abovedescribed, does not produce any appreciableor detrimental delay in theoperation of the corresponding receiving'instrument at the distant endof the line nor does it appreciably orv detrimentally shorten the signalwhether it be a dot or a dash.

The function of relays 11 and 12 of the transmitters is simply to sooperate the circuits connected to the corresponding transmittingkey 13that a pulsation of the current of the proper polarity will be producedin the line at the instant when the key is depressed and again at theinstant when the key is released; but I do not limit myself to the useof any particular devices for producing double pulses each timea key isdepressed and then released,

nor do I limit myself to the particular selecting devices'employed forgiving precedence to oneor the other of the pulses when two keys aredepressed simultaneously, although I believe the transmittinginstruments and the selector to be particularlysuitable for use in thissystem. The relays 11 may be termed primary relays of the transmittersand the relays 12 ,secondary relays. Thecircuits The receiving-relays Fand G at the receiv ing-station B may be termed single-directiondouble-current relays, since each responds to current impulses of butone direction, but is changed from and restored to normal condition byalternate current impulses of that direction. Each of the relaysconsists, essentially, of a polar relay provided with means forreversing the polarity of its armature when the position of saidarmature is reversed, so that a current impulse of the same direction asthe impulse which first defleeted the armature from its normal positionwill send it back to normal position; but in order to obtain greatdelicacy of operation and also steadiness I prefer to employ in therelay the principles employed in the polar relay covered by my PatentNo. 560,313, dated March 19, 1896that is to say, to employ a secondarycircuit which tends to hold the armature stationary, but is broken whenthe armature moves and is reversed when the position of the armature isreversed, and a tertiary circuit which normally opposes the secondarycircuit, but is weaker than the secondary circuit, and is reversed by areversingrelay controlled by said secondary circuit when the position ofthe main armature is reversed.

Each receiving-relay consists of three subrelays-viz., a main relay 30,through which the line-circuit passes, a secondary relay 31, and areversing-relay 32. The armatures of relays 30 and 31 are mechanicallyconnected, so as to move together, and may be connected in the mannershown diagrammatically, one having a rounded end fitting within a forkedend of the other, though I do not limit myself to their connection inthis manner. Relay 32 is an ordinary polar relay, having, however, aweighted armature, the weight being adjustable, as is the case with therelays 11 of the transmitters. Each receiving-relay has two localbatteries 33 and 34, the poles of which are oppositely placed. Thepositive pole of battery 33 is connected to the left-hand contact-stopof the connected armatures of relays 30 and 31 and is also connected tothe left-hand contact-st0p of relay 32. The negative pole of battery 34is similarly connected to the right-hand contact-stop of relay 32 and tothe right-hand contact-stop of relays 30 and 31 through a sounder orother receiving instrument, which is lettered O, for receiving relay Fand P for receiving relay Preferably a shuntresistance-coil is connectedacross the terminals of each sounder, as shown in the drawings. One ofthe two connected armatures of relays 30 and 31 is con nected to aconductor 35,leading through coils of relay 32 to a return-conductor 36,connected to a conductor 37, which connects the negative pole of battery33 and the positive pole of battery 34. W hen battery energizes thiscircuit of conductor 35, the armature of relay 32 is moved or held tothe left, and when battery 34 energizes the circuit said armature ismoved or held to the right. A branch conductor 38 leads from conductor35 through coils of relay 31 to return-conductor 36, and these coils ofrelay 31 when energized by battery 33 tend to hold the two connectedarmatures to the left, while when the coils are energized by battery 34they tend to hold the connected armatures to the right.

Relays 31 and 32 have their armatures magnetized by permanent magnets,or if their armatures be magnetized by elcctromagnets the polarity ofsuch magnets is never changed with respect to that of the main or lieldmagnets. The armature of relay 30, however, is magnetized by anclectroniagnet 39, the polarity of which is reversed by the relay 32when it operates, owing to the fact that relay 39 is energized bycurrent from whichever of thebatteries 33 or 34 is in comniunicationwith the armature of relay 32 and passing from said armature throughconductor 40, which is also connected to the coils of magnet 39 andthrough the return-00nductor 36. A branch conductor 41 leads fromconductor 40 through coils of relay 31, which opposes those to whichconductor 38 is connected, and through an adjusting-rhcostat 42 to thereturn-conductor 36. The resistance of the rheostat 42 is so adjustedthat the cfl'ect upon the connected armatures of the coils to whichconductor 36 is connected when said coils are \energized is almostneutralized by the ell'ect on said armatures of the coils to whichconductor 41 is connected, suiiicient of the magnetizing force of thecoils connected to the conductor 38 being left unneutralizcd, however,to hold the armatures stationary against the effects of leakage orinduction-currents in theline. Theline conductorL 'iasscs through thecoils of the main magnet of subrclay 30 of relay F and through thecorresponding coils of subrelay 30 of relay G to ground.

Conductors 35 and 38, passing through magnet-coils of subrelays 31 and32, together with conductors connecting the batteries 33 and 34 to thecontact-points oi the connected relays 30 and 31 and thercturn-comluctors, may be said to constitute a secondary circuit.Conductors 40 and 41, passing through magnet-coils of relay 31 andthrough the armature-magnet 39 of relay 30, together with the conductorsconnecting the batteries 33 and 34: to the contact-points of relay 32and the return-conductors, may be said to constitute a tertiary circuit.

A's willbe shown, each of the relays F and G responds only to thecurrents of one .po-

larity, being extremely sensitive, however,

larly. The magnet 39 of relay F is so wound.

' or so connected in its circuit that said relay circuit is broken, andthe effect of the tertiary circuit on the'armatures being then unopposedthe current in said tertiary circuit will carry the armatures over,eventhough the current pulsation in the line which primarily caused thearmatures to move should cease before they have reached the right-handcontact-stop. As soon as the armatures reach such stop the secondarycircuit is completed from battery 34 through sounder 0, thus operatingthe sounder, holding the connected armatures against their right-handcontactstop and reversing the armature of relay 32, so reversing thetertiary circuit, which when reversed again opposes the secondarycircuit in relay 31. The reversal of the armature of relay 32 reversesthe polarity of magnet 39, so that when a second positive pulse comesover the line the connected armatures of relays 30 and 31 will be movedto the left and relay 32 again reversed, thus cutting out the sounder Oandvrestoring the parts to their.

and when said armatures are against their right-hand stop, the polarityof magnet 39 having been reversed negative pulses in the line conductorsimply tend tohold the armatures in that position.

Tothe contact-stop of contact-lever 28.. of

selecting-relay M is connected a conductor 50, leading to ground. Whenthe armature 15 of said relay occupies an intermediate'position, thelineconductor L is connected through the armature and lever 28 to conductor50, and so' to ground. This ground connection facilitates the dischargeof the line after each signal.

The operation of the instruments and circuits shown in Fig. 1 is afollows: Normally the armatures of relays 1 and 2 of vibrator N are inrapid vibration. If one of the transmit terkeys-as, for instance, thatof transmitter Cbe depressed, a selector-circuit is'completed throughconductor 14 in this case and through conductor 21 of the transmitter,thus deflecting the armature of selecting-relay M to the left andplacing battery H to the line and arresting the vibration of armatures 3and 7 of the vibrator. Energizing the magnetcoils of relay 11, throughwhich conductor 21 passes, causes the armature of said relay to move tothe left, and when it has reached its left-handcontact-point itcompletes thelocal circuit of conductor 25 through battery 23, thusreversing the relay 12, breaking the selector-circuit of conductor 1 1,and ending the current impulse from battery H, the vibrator beginning tooperate again immediately.

When the transmitter-key is released, selectorcircuit 1 1 is againcompleted, this time through conductor 19, the battery H is again placedto the line by relay M, and the relay 11 is again reversed, thusreversing relay 12 and breaking the selector-circuit again, thus endingthe current impulse from battery H. 'In this way a brief current impulseis produced in the line at the beginning and again at the end of eachsignal of transmitter O, the length of the impulse being determined bythe adjustment of the weight on thearmature of relay 11 and the distancebetween the stops of said armatures. If transmitter D be operated, animpulse of current from batteryI passes through the line at thebeginning and again at the end of each signal of the transmitter. Bothselector-circuits'viz. the circuits of conductors 14 and 29cannot becomplete at the same instant, forsaid circuits pass through opposingcontacts of relay 1. Hence if the transmitter-keys of the twotransmitters be operated simultaneously that selector-circuit will becompleted first with the contact-point of which the armature 3 firstmakes contact, and as each impulse in each selector-circuit checks thevibration of the armature 3 the impluse in the other selector-circuitwill be delayed until the impulse in the selector-circuit firstcompleted is finished. In this way conflict between the two transmittersis avoided. The impulses are of such short duration, however, that theslight delay in the sending of an impulse by one transmitter under suchcircumstances is imperceptible, and the delay is never sufficient toconvert a dot into a dash. When an impulse Ice 4 of positive currentpasses through the line at the beginning of a signal of transmitter C,it deflects the connected armatures of relays 30 and 31 of receivinginstrument F to the right. The secondary circuit through conductor 31 isbroken the instant said armatures begin to move, so that the tertiarycircuit will carry the armatures ever even should the impulse ceasebefore the armatures have reached their right-h and con tact-point. Whenthey do reach said right-hand contact-point, the secondary circuit isagain completed, but with the current reversed, and the reversingrelay32 is reversed, thus reversing the direction of current in the tertiarycircuit and reversing the magnet 39, by which the armature of relay 30is magnetized. Negative impulses in the line can have no influence onrelay F When the parts are in this position therefore; but when asucceeding positive pulse passes through the line the armatures aredeflected back to their first positions by a similar action of thecircuits, magnet 39 recovering its former polarity. The completion ofthe secondary circuit through the right-hand contact-point of relays 30and 31 operates the sounder O. Receiving-relay G is operated in asimilar manner by negative current impulses, but does not respond topositive current impulses.

The receivingrelays are not aifected by leakage and induction-currentsin the line, since a line-current in order to operate either relay mustovercome, though but for an instant, that portion of the influence ofthe secondary circuit on the armatures of relays 30 and 31 which is notbalanced by the tertiary circuit.

In Fig. 2 the transmitting and receiving instruments at one end of aquadruplex line are shown. The transmitting instruments and circuits arethe same as those shown in Fig. 1. Since the receiving-stationcorresponds to a transmitting-station at the distant end of the line, itis lettered B. The receiving instruments are the same as those shown inFig. 1, except that each main relay is provided with two separate setsof coils, one connected to the line conductor L and the other to anartificial line conductor L. The effect of the artificial line is tobalance the influence of outgoing messages in the line upon the homereceiving instruments.

A great advantage of the system of duplex and quadruplex telegraphyherein described is that it employs nothing but pulsatory currents. Ihave found that much better results may be obtained by the use of suchcurrents than by the use of currents of longer duration. Arcing at thecontact-points is avoided, and it is possible to use a higher linepotential without excessive leakage than would be possible otherwise,thus insuring clearer signals. Another great advantage of this system isthat it employs nothing but polar instruments, which are far moreseiisitive. quick-acting, and reliable than instruments of the neutraltype.

For convenience in following the action of opposing magnet-coils ofcertain of the instruments herein illustrated 1 have sought in certaininstances as, for example, in the illustration of relay l to indicatethe opposing action of the several coils in each magnet-spool of therelay by showing the same wound in opposite directions about the core.It will be understood that such illustration is purely diagrammatic andillustrative and does not indicate any specilicdircction of winding.Furthermore, it has been necessary to avoid confusion of the drawings toshow correspending coils on opposite sides of the armatures of the saidrelays as wound in the same direction. It will be understood that in sodoing I illustrate merely therelative winding with respect to each coreconsidered separately of the coils surrounding the same and that theconnection of the several corresponding coils to their respectivecircuits must, nevertheless, be such that corresponding coils onopposite sides of an armature tend in every case to produce oppositemagnetic poles, as in any ordinary relay or horseshoe-electromagnet.

In another application for Letters Patent, filed October 11, 1898,Serial No. 693,205, of which this application is a division, I. haveillustrated, described, and claimed the apparatus herein illustrated anddescribed and which carries out the method of transmission hereindescribed and claimed.

hat I claim is 1. The herein-described method of trans mittingsimultaneous telegraphic messages in the same direction, through asingle circuit, which consists in transmitting the signals of eachmessage by current impulses occurring in pairs, one at the beginning andthe other at the end of each signal, the signals of one message beingtransmitted by positive impulses and the signals of the other message bynegative impulses.

2. The herein-described method of transmitting simultaneous telegraphicmessages in the same direction, through a single circuit, which consistsin transmitting the signals of each message by current impulsesoccurring in pairs, one at the beginning and the other at the end ofeach signal, the signals of one message being transmitted by positiveimpulses and the signals of the other message by negative impulses, andin giving precedence to an impulse of one signal over an impulse ofanother signal, when required.

3. The herein-described method of trans mitting simultaneous telegraphicmessages, through a single circuit, which consists in transmitting twomessages in each direction by current impulses occurring in pairs, oneat the beginning and the other at the end of each signal, the signals ofone message being trans- 7 mitted by positive impulses and the signalsof the other message by negative impulses, and in counteracting, ateachend of the line, the effect of the outgoing messages upon the receivinginstruments located at that end of the line, by a method of duplextelegraphy, substantially as described.

4:. The herein-described method of transmitting simultaneous telegraphicmessages, through a single circuit, which consists in transmitting twomessages in each direction by current impulses occurring in pairs, oneat the beginning and the other at the end of each signal, the signals ofone message being transmitted by positive impulses and the signals ofthe other message being transmitted by negative impulses, in givingprecedence to an impulse of one signal over an impulse of anothersignal, when required, and in counteracting, at each end of the line,the effect of the outgoing messages upon the receiving instrumentslocated at that end of the line, by a method of duplex telegraphy,substantially as described.

5. The herein-described method of transmitting telegraphic/signals,which consists in transmitting signals by current impulses always of thesame polarity, which occur in pairs, one at the beginning and the otherat the end of each signal, each signal, dot or dash, as the case may be,comprising two such impulses, the duration of the interval between theimpulses of each signal determining whether that signal is a dot or adash,

In testimony whereof I aflix my signature in the presence of twowitnesses.

THOMAS B. DIXON.

Witnesses:

' HARRY M. MARBLE,

A. H. PERLES.

